Why ESXi Installation Only Uses Half of SSD Storage

I don't understand why you're only able to use 1TB but I suspect it's due to ESX/i's 2TB-per-LUN limit - basically you can't have a single VMFS extent larger than 2TB nor can it address a larger than 2TB LUN properly - carve your iSCSI LUNs into <2TB and try that again.

As for the problem you face, well if ESXi doesn't 'see' it then you're safe to do what you like from the LaCie perspective - i.e. reboot it as it appears to still be locked. This may just be an incompatibility issue, no LaCie storage products are on the VMWare Hardware Compatibility List I'm afraid.

A silent ESXi server, well there's a first time for everything I guess - are you sure this is for a professional/production system? I'd be really interested in what you're doing here.

Anyway it seems a bit odd to be a) using an SSD as your main datastore at all and b) worrying about storage performance when you'll be using a passively cooled CPU (presumably). Unless you know SSDs are the right solution for you and that your full end to end system will benefit from the extra performance these higher-end SSDs then I'd go for pretty much any of them but with an emphasis on choosing the one with the most over-commit memory.